Incubation of membranes with S-adenosylmethionine, acyl coenzyme A, and FeSO4 results in the formation of S-methyl-acylthioester. This is a novel reaction which could participate in drug metabolism. Pantethine, a metabolic precursor for coenzyme A, depletes cystinotic cells of cystine. This could provide a safe, effective treatment for cystinosis. Bovine retina incorporates palmitate into rhodopsin.